Fix validation error when field is disabled

If a selectfield is disabled, None is returned (not a string).
To pass wtforms validation, that value shall be part of the choices.

We use None as the value for SelectField that are optional (instead of
'').
We were previously converting '' to None when creating a model.
We now use the coerce function to let the form convert 'None' to None.

app/inventory/forms.py

@@ -33,11 +33,11 @@ class ItemForm(FlaskForm):
                                      validators.Regexp(models.ICS_ID_RE)])
     serial_number = StringField('Serial number',
                                 validators=[validators.InputRequired()])
-    manufacturer_id = SelectField('Manufacturer')
-    model_id = SelectField('Model')
-    location_id = SelectField('Location')
-    status_id = SelectField('Status')
-    parent_id = SelectField('Parent')
+    manufacturer_id = SelectField('Manufacturer', coerce=utils.coerce_to_str_or_none)
+    model_id = SelectField('Model', coerce=utils.coerce_to_str_or_none)
+    location_id = SelectField('Location', coerce=utils.coerce_to_str_or_none)
+    status_id = SelectField('Status', coerce=utils.coerce_to_str_or_none)
+    parent_id = SelectField('Parent', coerce=utils.coerce_to_str_or_none)
     mac_addresses = StringField(
         'MAC addresses',
         description='space separated list of MAC addresses',
@@ -45,11 +45,11 @@ class ItemForm(FlaskForm):
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
-        self.manufacturer_id.choices = utils.get_model_choices(models.Manufacturer, allow_blank=True)
-        self.model_id.choices = utils.get_model_choices(models.Model, allow_blank=True)
-        self.location_id.choices = utils.get_model_choices(models.Location, allow_blank=True)
-        self.status_id.choices = utils.get_model_choices(models.Status, allow_blank=True)
-        self.parent_id.choices = utils.get_model_choices(models.Item, allow_blank=True, attr='ics_id')
+        self.manufacturer_id.choices = utils.get_model_choices(models.Manufacturer, allow_none=True)
+        self.model_id.choices = utils.get_model_choices(models.Model, allow_none=True)
+        self.location_id.choices = utils.get_model_choices(models.Location, allow_none=True)
+        self.status_id.choices = utils.get_model_choices(models.Status, allow_none=True)
+        self.parent_id.choices = utils.get_model_choices(models.Item, allow_none=True, attr='ics_id')
 
 
 class CommentForm(FlaskForm):

app/inventory/views.py

@@ -58,11 +58,11 @@ def create_item():
             session[key] = getattr(form, key).data
         item = models.Item(ics_id=form.ics_id.data,
                            serial_number=form.serial_number.data,
-                           manufacturer_id=form.manufacturer_id.data or None,
-                           model_id=form.model_id.data or None,
-                           location_id=form.location_id.data or None,
-                           status_id=form.status_id.data or None,
-                           parent_id=form.parent_id.data or None)
+                           manufacturer_id=form.manufacturer_id.data,
+                           model_id=form.model_id.data,
+                           location_id=form.location_id.data,
+                           status_id=form.status_id.data,
+                           parent_id=form.parent_id.data)
         item.macs = [models.Mac(address=address) for address in form.mac_addresses.data.split()]
         current_app.logger.debug(f'Trying to create: {item!r}')
         db.session.add(item)
@@ -109,7 +109,7 @@ def edit_item(ics_id):
     if form.validate_on_submit():
         item.serial_number = form.serial_number.data
         for key in ('manufacturer_id', 'model_id', 'location_id', 'status_id', 'parent_id'):
-            setattr(item, key, getattr(form, key).data or None)
+            setattr(item, key, getattr(form, key).data)
         new_addresses = form.mac_addresses.data.split()
         # Delete the MAC addresses that have been removed
         for (index, mac) in enumerate(item.macs):

app/networks/forms.py

@@ -34,7 +34,7 @@ class HostForm(FlaskForm):
                        filters=[utils.lowercase_field])
     type = SelectField('Type', choices=utils.get_choices(('Virtual', 'Physical')))
     description = TextAreaField('Description')
-    item_id = SelectField('Item')
+    item_id = SelectField('Item', coerce=utils.coerce_to_str_or_none)
     network_id = SelectField('Network')
     # The list of IPs is dynamically created on the browser side
     # depending on the selected network
@@ -44,10 +44,10 @@ class HostForm(FlaskForm):
         description='name must be 2-20 characters long and contain only letters, numbers and dash',
         validators=[validators.InputRequired(), validators.Regexp(models.HOST_NAME_RE)],
         filters=[utils.lowercase_field])
-    mac_id = SelectField('MAC')
+    mac_id = SelectField('MAC', coerce=utils.coerce_to_str_or_none)
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
-        self.item_id.choices = utils.get_model_choices(models.Item, allow_blank=True, attr='ics_id')
-        self.network_id.choices = utils.get_model_choices(models.Network, allow_blank=False, attr='vlan_name')
-        self.mac_id.choices = utils.get_model_choices(models.Mac, allow_blank=True, attr='address')
+        self.item_id.choices = utils.get_model_choices(models.Item, allow_none=True, attr='ics_id')
+        self.network_id.choices = utils.get_model_choices(models.Network, allow_none=False, attr='vlan_name')
+        self.mac_id.choices = utils.get_model_choices(models.Mac, allow_none=True, attr='address')

app/networks/views.py

@@ -44,12 +44,12 @@ def create_host():
         host = models.Host(name=form.name.data,
                            type=form.type.data,
                            description=form.description.data or None,
-                           item_id=form.item_id.data or None)
+                           item_id=form.item_id.data)
         host.interfaces = [
             models.Interface(name=form.interface_name.data,
                              ip=form.ip.data,
                              network_id=network_id,
-                             mac_id=form.mac_id.data or None)
+                             mac_id=form.mac_id.data)
         ]
         current_app.logger.debug(f'Trying to create: {host!r}')
         db.session.add(host)

app/utils.py

@@ -107,11 +107,11 @@ def get_choices(iterable, allow_blank=False, allow_null=False):
     return choices
 
 
-def get_model_choices(model, allow_blank=False, attr='name'):
+def get_model_choices(model, allow_none=False, attr='name'):
     """Return a list of (value, label)"""
     choices = []
-    if allow_blank:
-        choices = [('', '')]
+    if allow_none:
+        choices = [(None, '')]
     choices.extend([(str(instance.id), getattr(instance, attr)) for instance in model.query.all()])
     return choices
 
@@ -138,3 +138,15 @@ def lowercase_field(value):
         return value.lower()
     except AttributeError:
         return value
+
+
+# coerce function to use with SelectField that can accept a None value
+# wtforms always coerce to string by default
+# Values returned from the form are usually strings but if a field is disabled
+# None is returned
+# To pass wtforms validation, the value returned must be part of choices
+def coerce_to_str_or_none(value):
+    """Convert '', None and 'None' to None"""
+    if not value or value == 'None':
+        return None
+    return str(value)